Transdermal patches

Question 1

What are advantages and disadvantages of TD delivery

Answer 1

Advantages
- Avoids GI drug absorption difficulties
* Alternative to oral or parenteral administration
* Avoids first-pass metabolism
* Multi-day therapy can be achieved by a single application (good with adherence)
* Extends the activity of drugs with short half-lives
* Easy to terminate the drug’s effect

Disadvantages
- Unsuitable for drugs that sensitize the skin
- Only relatively potent drugs can be used
- Adhesion of the transdermal delivery system to the skin may be variable

Question 2

What are ideal parameters for candidates of transdermal delivery?

Answer 2

• hydrophobic (logP = +1-3)
• Lowest Molecular weight less than 500
• low melting point (less than 200 C)
• pH of saturated aqueous solution 5-9
• Deliverable dose < 10mg/day

Question 3

What are the type of transdermal pathces and what are their proerpties (3)

Answer 3

1. Reservoir type
   - rate controlling membrane
2. Matrix type
   - Rate controlling in matrix and SC (no membrane)
   - Adhesive on perimeter (nitroglycerin for angina) on entire surface (nicoderm)
3. Drug-in-adhesive
   - Monolithic
   - Multilaminate
   - Rate controlling adhesive matrix (entire surface)
   - First order kinetics of drug release (release proportional to drug concentration within the
   adhesive)
   - Can cut to adjust dose
   - single layer DIA (no membrane), multi-layer DIA (membrane)

Question 4

What are main safety issues with patches?

Answer 4

• Confusion factor
• Improper application
• Nomenclature issues
• Dosing intervals
• Pediatric patches
• Physician errors
• Self-storage

Question 5

Which type of TD patch is the least safest for fentanyl

Answer 5

• Reservoir patches
• can puncture and dose
  dumping can occur which can cause overdose and respiratory failure

Question 6

What is the rationale for using Dermal Therapeutic Systems (DTS) and what type of DTS do you know?

Answer 6

• maximize delivery of drug into epidermis or dermis, while minimizing further absorption into systemic circulation

Types
- Emla
- Treatment of corns, calluses, warts
- Cosmetic patches
- NSAIDs (inflammation)

Question 7

What is the rationale for using Dermal Therapeutic Systems (DTS) and what type of DTS do you know?

Answer 7

• maximize delivery of drug into epidermis or dermis, while minimizing further absorption into systemic circulation

Types
- Emla
- Treatment of corns, calluses, warts
- Cosmetic patches
- NSAIDs (inflammation)